In battery management, it is always needed to monitor the status of a battery, such as the voltage of the battery, by Analog Front End (AFE) devices. The analog front end device is coupled to the battery and accesses digital data regarding status, such as voltage of the battery. The digital data will be transferred to the microprocessor for various purposes, such as coulomb counting or protection purpose.
With increasing the number of the cells of the stacked battery, the voltage of the stacked battery will become higher and higher. Further, the voltage capacity of analog front end device is limited by the pin count of the AFE device or the physical process breakdown voltage of the AFE device. In this case, only one analog front end device will not be able to monitor the whole stacked battery. Therefore, a plurality of analog front end devices are used to monitor the status of the stacked battery and it is needed to establish a communication path between the microprocessor and each analog front end device.
Referring to Prior Art FIG. 1, it shows a block diagram of a communication construction or a bus 10 between a stacked battery 20 and a microprocessor 15. The stacked battery comprises a plurality of battery blocks or packs, 22, 24, . . . and 26. A plurality of analog front end devices 12, 14 . . . and 16 are stacked and are coupled to the battery packs 22, 24 . . . and 26, respectively, for monitoring the status of each of the battery packs 22, 24 . . . and 26. In other words, each of the analog front end devices 12, 14 . . . and 16 only monitors a portion of the stacked battery 20. A bus 10 is coupled to the analog front end devices 12, 14 . . . and 16. It has been found that the analog front end devices 12, 14 . . . and 16 do not have a common ground voltage and, as such, the varied ground voltages need to be isolated. Conventionally, a coupling device, such as optical coupler, inductor or capacitor, is used to establish an external communication path between the AFE blocks 12, 14 . . . and 16 and the microprocessor 15. The non-common ground signal is transferred through the coupling devices, such as optical couplers, inductors or capacitors. Those approaches are complex and expensive.